Atlas V 531

The Atlas V 531 Launch Vehicle is a part of the flight proven Atlas V 400/500 family that is being operated by United Launch Alliance. Atlas V rockets are flown since 2002 and have a near-perfect success rate (one flight was a partial failure, however the mission was catalogued as a success).

The Vehicle is operated from Launch Complex 41 at the Cape Canaveral Air Force Station, Florida and Launch Complex 3E at Vandenberg Air Force Base, California. The vehicle is assembled in Decatur, Alabama; Harlingen, Texas; San Diego, California; and at United Launch Alliance's headquarters near Denver, Colorado.Atlas V 531 features three Solid Rocket Boosters installed on a Common Core Booster with a common single engine Centaur on top and a 5.4-meter Payload Fairing. Centaur can make multiple burns to deliver payloads to a variety of orbits including Low and Medium Earth Orbit, Geostationary Transfer Orbit and Geostationary Orbit as well as Earth Escape Trajectories.To date, Atlas V 531 has only been used to deliver AEHF (Advanced Extremely High Frequency) Communications Satellites to Geostationary Transfer Orbit. The modular design of Atlas V allows the vehicle to be built to the specific performance requirements of each mission by adding boosters.Every Atlas V version has a three digit ID-Number:First Digit: Payload Fairing diameter: 4XX - 4m Diameter; 5XX - 5.4m DiameterSecond Digit: Number of Solid Rocket Boosters (0-5)Third Digit: Number of RL-10A Engines on Centaur (1 or 2)

Photo: United Launch Alliance

Atlas V 531 Specifications

Type

Atlas V 531

Height

62.2m

Diameter

3.81m

Launch Mass

475,000kg

Stage 1

Atlas Common Core Booster

Boosters

Three

Span

6.9m

Stage 2

Centaur

Mass to LEO

15,575kg

Mass to SSO

11,160kg

Mass to GTO

7,475kg

Mass to GEO

3,250kg

First Stage

Type

Common Core Booster

Inert
Mass

21,054kg

Diameter

3.81m

Length

32.46m

Propellant

Rocket
Propellant-1 (Kerosene)

Oxidizer

Liquid Oxygen

Fuel&Oxidizer
Mass

284,089kg

Guidance

From Centaur

Propulsion

RD-180 Engine (2
Chambers)

Type

Staged Combustion

Thrust at
Sea Level

3,827kN

Isp SL

311s

Thrust
(Vacuum)

4,152kN (933,369
lbf)

Isp Vac

338s

Egnine
Length

3.56m

Engine
Diameter

3.15m

Engine
Dry Weight

5,480kg

Chamber
Pressure

266.8bar

Nozzle
Ratio

36.87

Thrust to
Weight

78.22

Area
Ratio

36.4

Ox. To
Fuel Ratio

2.72

Attitude
Control

Gimbaled Engine
(8 Degrees)

Throttle
Capability

50-100%

Burn Time

253 sec

Tank
Pressurization

Helium

Avionics

Flight Control,
Flight Termination

Telemetry, Rate
Gyros, Power

Stage
Separation

8 Retro Rockets

Photo: NASA

Solid Rocket Boosters

# Boosters

Three

Manufacturer

Aerojet

Ignition

Ground-Lit

Length

20m

Diameter

1.58m

Inert Mass

5,740kg

Launch Mass

46,697kg

Thrust

1,688.4kN

Specific Impulse

279s

Nozzle Cant

3°

Burn
Time

94sec

Interstage Adapter

Type

Cylindrical Interstage Adapter

Diameter

3.83m

Length

0.32m

Mass

285kg

Structure

Aluminum Machined

Rolled-Ring Forging

C-ISA Adapter

Diameter

3.83m

Length

3.81m

Components

Interstage Adapter

Aft Stub Adapter

Boattail

Mass

2,212kg

Structure

Composite Sandwich

Aluminum Core

Graphite Epoxy Face Sheets

Centaur Upper Stage

Type

Centaur

Diameter

3.05m

Length

12.68m

Inert
Mass

2,243kg

Propellant

Liquid Hydrogen

Oxidizer

Liquid Oxygen

Fuel&Oxidizer
Mass

20,830kg

Guidance

Inertial

Propulsion

1 RL 10A-4-2

Thrust

99.2kN

Isp Vac

451s

Engine
Length

3.53m

Engine
Diameter

1.53m

Engine
Dry Weight

167kg

Chamber
Pressure

39bar

Thrust to
Weight

61

Area
Ratio

84

Burn Time

Variable

Engine
Start

Restartable

Attitude
control

4 27-N Thrusters

8 40-N Thrusters

Propellant

Hydrazine

Photo: Pratt&Whitney Rocketdyne

Payload Fairing

Fairing

Bisector, Sandwich Construction

Epoxy Face Sheets

Aluminum Honeycomb Core

Boattail

Fixed, Composite Sandwich

Separation

Linear Piston & Cylinder
activated

by Pyro Cord, Expanding Tube

shearing a notched Frame for

Horizontal Separation

Type

Short PLF

Diameter

5.4m

Length

20.7m

Mass

3,524kg

Type

Medium PLF

Diameter

5.4m

Length

23.4m

Mass

4,003kg

Type

Long PLF

Diameter

5.4m

Length

26.5m

Mass

4,379kg

Photo: United Launch Alliance

Launch Vehicle Description

Atlas V 531 stands 62.2 meters tall and has a main diameter of 3.81 meters. With a liftoff mass of 475,000 Kilograms. The Launcher uses the conventional Atlas V design with a Common Core Booster and a Centaur Upper Stage on top of it, plus three Solid Rocket Boosters on the CCB.

Atlas V 531 features a 5.4-meter payload Fairing under which it can carry payloads of up to 15,575 Kilograms to Low Earth Orbit. Geostationary Transfer Orbit Capability is 7,475 Kilograms. Direct GEO Injections of Payloads up to 3,250kg are also possible.

Photo: United Launch Alliance

Common Core Booster

The first Stage of the Atlas V 531 is an Atlas Common Core Booster that is 32.46 meters long and has a diameter of 3.81 meters. With an inert mass of 21,054 Kilograms, the Common Core booster can hold up to 284,089 Kilograms of Rocket Propellant-1 and Liquid Oxygen that are consumed by the single RD-180 Main Engine of the vehicle.

RD-180 is being manufactured by NPO Energomash. It is a two-chamber staged combustion engine that provides 3,827 Kilonewtons of liftoff thrust and 4,152 Kilonewtons of vacuum thrust. RD-180 maintains a high-pressure staged combustion cycle employing an Oxygen-rich preburner. It runs with an oxidizer to fuel ratio of 2.72. The drawback of an oxygen-rich combustion is that high pressure, high temperature gaseous oxygen must be transported throughout the engine. The nominal chamber pressure is 267 bar. RD-180 is capable of being throttled from 50% to 100% of rated performance. The engine is based on the RD-170 engine that features four combustion chambers. First Stage control is accomplished by gimbaling the RD-180 nozzles by up to 8 degrees. Engine gimbaling is achieved via the vehicles hydraulics system.

The first stage propellants are held inside aluminum isogrid tanks; tank pressurization is accomplished with high-pressure Helium that is stored in Helium Bottles on the Common Core Booster. Tank pressurization is computer-controlled. The Common Core Booster is equipped with a Flight Termination System that can be used to destroy the vehicle in the event of any major malfunction. Also, the CCB is outfitted with redundant Rate Gyros to acquire navigation data. Internal Batteries provide power during powered ascent and an independent telemetry system is utilized for data downlink. First stage separation is initiated by pyrotechnics and the core stage ignites eight retro rockets to drop away from the launcher.

Photo: NASA Kennedy

Solid Rocket Boosters

Atlas V 531 is equipped with three Aerojet Solid Rocket Boosters that are all ignited at the moment of T-0 to provide extra thrust to lift the heavy launch vehicle with a total Thrust-To-Weight Ratio of 1.90. Each of the Boosters has an inert mass of about 5,740kg and a total fuel load of nearly 41,000kg. The Booster provides a thrust of 1,688kN - 172,200 Kilograms. The five boosters burn for 94 seconds and are separated in a staged fashion by firing pyrotechnic initiators. First, boosters 1&2 that are installed on one side of the vehicle are separated followed about 1.5 seconds later by booster 3. Typically, the boosters burn out at T+94 seconds, but the vehicle holds onto the boosters for another 15 seconds for Range Safety Reasons to ensure an impact in the pre-planned off-shore area.

Photo: NASA Kennedy

Photo: NASA Kennedy

Interstage Adapter

The first and second stage of the Atlas V launch vehicle are connected by a Interstage Adapter that is used to join the two stages of the vehicle that feature different diameters. It consists of a cylindrical section that is 3.83 meters in diameter and 0.32 meters in length. The structure consists of Aluminum and weighs 285 Kilograms.

Centaur Upper Stage

The Upper Stage of the Atlas V 531 is a single-engine Centaur Stage. Centaur is 3.05 meters in diameter and 12.68 meters in length with an inert mass of 2,243 Kilograms. Centaur is a cryogenic rocket stage using Liquid Hydrogen and Liquid Oxygen as propellants. A total of 20,830 Kilograms of propellants can be filled into the vehicle's pressure stabilized stainless steel tanks. The LOX and LH2 Tanks are separated by a common ellipsoidal bulkhead.

Centaur is powered by a RL-10A-4-2 engine that is manufactured by Pratt & Whitney Rocketdyne and provides 99.2 Kilonewtons of thrust. The engine uses an expander cycle and operates at a chamber pressure of 39 bar. It is 3.53 meters in length, 1.53 meters in diameter and features a Nozzle Extension. RL-10 has a certified burn time of up to 740 seconds and can make multiple engine starts. It has a dry weight of 166 Kilograms and an expansion ratio of 84:1 achieving a thrust to weight ratio of 61:1. RL-10 can be gimbaled with a electromechanical system to provide vehicle control during powered flight. During Coast Phases, the vehicle's orientation is controlled by Centaur's Reaction Control System. Eight lateral 40-Newton Thrusters and four 27-Newton Thrusters are used for attitude control. The System uses Hydrazine propellant. The Centaur Upper Stage houses the Atlas V Flight and Guidance Computers that are capable of autonomously performing the mission controlling all aspects of the flight. The fault-tolerant inertial navigation unit is located on the Centaur forward equipment module.

In the aft section of the Centaur Upper stage is an C-ISA - Centaur Interstage Adapter that is 3.83 meters in diameter and 3.81 meter in length. It includes three major components: Interstage Adapter, Aft Stub Adapter and Boattail. The adapter weighs 2,212kg for the single-engine upper stage.

Photo: NASA Kennedy

Payload Adapter

Payload Adapters interface with the vehicle and the payload and are the only attachment point of the payload on the Launcher. They provide equipment needed for spacecraft separation and connections for communications between the Upper Stage and the Payload. The separation system can be based on either the traditional pyrotechnical-initiated bolt cutters/separation nuts or Low-Shock Marmon Type Clamp Band Separation System. For Atlas V, a Launch Vehicle Adapter interfaces with the SIP (Standard Interface Plane) of the Launcher and connects to the Standard Payload Adapter or custom-made adapters. Four off-the-shelf adapters are available to accommodate various payloads. Also, custom made fairings can be fitted atop the Launch Vehicle Adapters to accommodate a variety off different payload requirements.

Payload Fairing

The Payload Fairing is positioned on top of the stacked vehicle and its integrated Payload. It protects the spacecraft against aerodynamic, thermal and acoustic environments that the vehicle experiences during atmospheric flight. When the launcher has left the atmosphere, the fairing is jettisoned by pyrotechnical initiated systems. Separating the fairing as early as possible increases launcher performance. The Atlas V 531 Rocket features fairings with a diameter of 5.4 meters.

Three different fairing lengths are available: 20.7, 23.4 and 26.5 meters. Major sections of these payload fairings are the boattail, the cylindrical section, and the nose cone that is topped by a spherical cap. Both fairing and boattail sections consists of Aluminum Skin Stringers and Frame Clampshells. The fairing is separated by a Linear Piston and Cylinder activated by a pyrotechnic cord to achieve vertical separation. Horizontal separation is accomplished with an expanding tube shearing a notched frame initiated by a pyrotechnic core. Payload Fairings are outfitted with acoustic panels, access doors and RF windows. Optional fairing hardware includes thermal shields and ECS doors. Also, the Payload Fairing is connected to a purge air system to ensure a controlled environment

Atlas V 531 Configuration

Image: United Launch Alliance

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